Engineering Commons^™

The Electrochemical Behaviors Of Superoxide Dismutase At Promoter Modified Gold Electrode, Xia-Qin Wu, Xiao-Yun Meng, Zhe-Su Wang, Zong-Rang Zhang

Journal of Electrochemistry

The electron-transfer process of superoxide dismutase was investigated by cyclic voltammetry at the 4,4'-dithiodipyridine, L-cysteine, histidine and arginine modified gold wire electrodes repectively. The quasi-reversible behavior was observed at L-cysteine modified gold electrode. An irreversible electrochemical behavior has been observed at hisdinine modified gold wire electrode.

Electro-Oxidation Of Phenol On Sno2/Ti Electrodes Prepared By Thermal Oxidation, Qing-Song Zhang, Hui-Huang Wu

Journal of Electrochemistry

A SnO₂/Ti electrode prepared by thermal oxidation was used as the anode for galvanostatic electrolysis in acidic solution containing phenol, the time-dependances of phenol concentration, chemical oxygen demand in solution(COD) and instantaneous current efficiency were determined during electrolysis. The results show that with the SnO₂/Ti anode instead of Pt, the COD significantly decreases at the same charge passage, and average current efficiency of oxidation increases by three times. The mechanism for phenol oxidation at two electrodes was discussed.

Studies On Methods Of Fuel Cells Electrodes Preparation, Jun Gu, Sheng Sui, Guang-Qiang Li, Zhitong Sui

Journal of Electrochemistry

In fuel cells, the structure of electrodes is an important factor which effect the cell performance. To improve the structure and the performance of electrodes, a new method of providing fuel cell electrodes is proposed in this paper. PTFE (polytetrafluoroethylene) and ethyne black was ground for about half an hour in a high-speed grinder, then the catalyst was added into the grinder and milled for an hour. This milled catalyst was transferred into a mixer followed by the addition of surface-active agent. After a suspension was formed, it was filtered under vacuum condition.Then a thin uniform filter-cake of the catalyst …

Study On Electrochemical Reduction Properties Of Nitrobenzene, Chu-Na Ma, Wen-Kui Zhang, Hui Huang, Yong-Ping Gan

Journal of Electrochemistry

The electrochemical reduction characteristics of nitrobenzene was extensively investigated by using the techniques such as quasi-steady-state polarization, cyclic voltammetry, fast linear potential sweep method and chronoamperometry in this paper. The electroanalytic properties of Cu, Cu-Hg and Cu-Ni electrodes were evaluated. Based on the study of the transient steping behaviour of nitrobenzene to PAP, the reduction mechanism was discussed. The results showed that the transition steps existed on the electrochemical reduction of nitrobenzene in acidic solution, the reactant is also absorbed on electrodes surface. The control step in the reduction of nitrobenzene was ascribed to the diffusion of nitrobenzene and its …

High Performance Proton Exchange Membrane Fuel Cells, Jing-Rong Yu, Bao-Lian Yi, Ming Han, Xiao-Liang Cheng, Zhi-Gang Shao, Jing-Xin Zhang

Journal of Electrochemistry

Proton-exchange membrane fuel cells(PEMFC) using a perfluorosulfonic acid proton exchange membrane as an electrolyte can simplify water and electrolyte management. In this paper, the effects of thickness of PEM on the performance of PEMFC were studied. The Nafion-112 PEM and low platinum loading E-TEK electrode yielded very high power density, of the order of 0.95 W/cm². The energy-conversion efficiency, the degree of platinum utilization and stability for PEMFC using Nafion 112 and E-TEK electrode were also investigated.

Photoelectrochemical Studies On The Tio2 Nanostructured Porous Film Sensitized By Cyanine Dye, Li Zhang, Mai-Zhi Yang, Xue-Bin Qiao, Yan-Zhong Hao, En-Qing Gao, Sheng-Min Cai

Journal of Electrochemistry

The photoelectrochemical behaviors of the TiO₂ nanostructured porous film sensitized by cyanine dye were investigated in this paper. The results showed that the excitaed state level matched the conduction band edge of TiO₂ nanoparticle. Therefore the sensitization of the dye can increase the photocurrent intensity of the TiO₂ nanostructured electrode obviously and results in a red-shift of optical absorption from the ultra-violet region to the visible. As a result, the light-to-electricity conversion efficiency was improved evidently, the maximum value of IPCE has reached 12.1%.

Investigation Of Sodium Hypophosphite Anodic Oxidizing Behavior In The Process Of Acid Electroless Nickel Deposition, Mei-Yuan Wang, Ya-Fei Kuang, Yan Xu

Journal of Electrochemistry

The anodic oxidizing behavior of sodium hypophosphite in the process of electroless nickle deposition (pH=5.5) was investigated with the linear potential sweep method and alternating current impedance. The results indicated that, the oxidation of NaH₂PO₂ was a complicated electrochemical process and affected by the concentration of NaH₂PO₂, the temperature of the bath, the sweep rate and the existence of nickel ion. The NaH₂PO₂ electrooxidation reaction was very likely preceded by heterogeneous interface transformation process, which might be the control step of the whole anodic process.

Studies Of The Electrode Preparation Of Electrode From Lead Carbonate For Lead Acid Batteryⅰ. The Activation Of The Pme, Zhong-Xu Dai, Di-Hua Wang, Jun-Wei Jiang, Yun-Hong Zhou, Jin-Yun Zou

Journal of Electrochemistry

Lead carbonate which was an intermediate product in lead hydrometallurgy without pollution of lead vapor and sulfur dioxide was selected as electrode material of lead-acid batteries. In the present work, the performances of PbO₂/PbSO₄ or PbSO₄/Pb electrode transformed from PbCO₃ have been investigated by powder microelectrode technique combined with cyclic voltammetry. The results show that the CV characteristics of either negative or positive electrode prepared from PbCO₃ is as good as that of both electrodes made from lead oxide produced by mill machine,when a powder microelectrode with PbCO₃ transformed into PbSO 4 …

Method For Testing Field Programmable Gate Arrays, Charles E. Stroud, Miron Abramovici

Electrical and Computer Engineering Faculty Patents

A method of testing field programmable gate arrays (FPGAs) includes the step of configuring programmable logic blocks of the FPGAs for completing a built-in self-test. Specifically, the FPGA under test may be configured to act as an iterative logic array wherein a first group of programmable logic blocks are configured as test pattern generators, output response analyzers and helper cells, and a second group of programmable logic blocks are configured as blocks under test. The blocks under test are then repeatedly reconfigured in order to completely test each block under test in all possible modes of operation. The first and …

Method Of Arc Welding Using Dual Serial Opposed Torches, Yuming Zhang, Shaobin Zhang

Electrical and Computer Engineering Faculty Patents

An improved method of arc welding uses a single power supply connected to opposed welding torches placed on both sides of a workpiece. Each torch is connected to a different polarity lead of the power supply and forms a separate arc with the workpiece. When a current is supplied to the first torch, it is guided from the first electrode, through the first arc, the workpiece, the second arc, and to the electrode of the second torch. This guiding function improves the penetration, concentration, as well as the directional stability of the arc. This permits the effective and efficient welding …

Electroluminescent Device Comprising A Transparent Structured Electrode Layer Made From A Conductive Polymer, Aemilianus G. J. Staring, David Braun

Electrical Engineering

A description is given of an electroluminescent (EL) device (1) composed of polymeric LEDs comprising an active layer (7) of a conjugated polymer and a transparent polymeric electrode layer (5) having electroconductive areas (51) as electrodes. Like the active layer (7), the electrode layer (5) can be manufactured in a simple manner by spin coating. The electrode layer (5) is structured into conductive electrodes (51) by exposure to UV light. The electrodes (9) and (51) jointly form a matrix of LEDs for a display. When a flexible substrate (3) is used, a very bendable EL device is obtained.

Accuracy Of Scatterometer-Derived Winds Using The Cramer-Rao Bound, David G. Long, Travis E. Oliphant

Faculty Publications

A wind scatterometer makes measurements of the normalized radar-backscatter coefficient O of the ocean surface. To retrieve the wind, a geophysical model function (GMF), which relates O to the near-surface wind, is used. The wind vector can be estimated using maximum-likelihood techniques from several O measurements made at different azimuth angles. The probability density of the measured O is assumed to be Gaussian with a variance that depends on the true O and therefore, depends on the wind through the GMF. With this model for wind estimation, the Cramer-Rao (C-R) bound is derived for wind estimation, and its implications for …

Crossover Photonic Switching Network With Cmos/Seed Smart Pixel Device And 2d Optical Fiber Bundle Array, Fengguang Luo, Mingcui Cao, Qiaoyan Hu, Anjun Wan, Jun Xu, Cong Deng, Deming Liu

Electro-Optics and Photonics Faculty Publications

A 16 X 16 Crossover photonic switching network with hybrid integrated CMOS/SEED smart pixel device and 2D optical fiber bundle array I/O access device is reported in this paper. SEEd array devices ar used as light receivers and transmitters, while CMOS devices make efficient logical processing. 4 X 40 2D multilayer optical fiber bundle arrays are fabricated and are used as I/O access devices in the crossover photonic switching network. The center to center spacing between adjacent optical fibers in the same layer of the fiber array is 125micrometers , and the spacing between adjacent layers is 250micrometers . Displacing …

Piezoelectric Doping In Alingan/Gan Heterostructures, M. Asif Khan, J. W. Yang, Grigory Simin, R. Gaska, M. S. Shur, A. D. Bykovski

Faculty Publications

We report on the piezoelectricdoping and two-dimensional (2D) electron mobility in AlInGaN/GaN heterostructures grown on 6H–SiC substrates. The contribution of piezoelectricdoping to the sheet electron density was determined using an In-controlled built-in strain-modulation technique. Our results demonstrate that in strained AlGaN/GaN heterostructures, the piezoelectric field generates at least 50% of the 2D electrons. The strain modulation changes the potential distribution at the heterointerface, which, in turn, strongly affects the 2D electron mobility, especially at cryogenic temperatures. The obtained results demonstrate the potential of strain engineering and piezoelectricdoping for GaN-based electronics.

Low-Frequency Noise In N-Gan With High Electron Mobility, M. E. Levinshtein, S. L. Rumyantsev, D. C. Look, R. J. Molnar, M. Asif Khan, Grigory Simin, V. Adivarahan, M. S. Shur

Faculty Publications

We report on the results of measurements of low frequency noise in n-type gallium nitride (GaN) grown on sapphire with 300 K electron mobility of 790 cm²/V s. The noise spectra have the form of 1/f noise with a Hooge parameter α of approximately 5×10⁻². This value of α is two orders of magnitude smaller than that observed before in n-GaN. The obtained results show that the level of flicker noise in GaN, just like that in GaAs and Si, strongly depends on the structural perfection of the material (the amplitude of the 1/f …

Coulomb Crystals And Glasses For Self-Assembly Of Nanoparticles, P. F. Williams, A. Belolipetski, A. Goussev, M. E. Markes

P. F. (Paul Frazer) Williams Publications

Under proper conditions, small particles may be suspended in a regularly-spaced array called a Coulomb crystal. In this paper we discuss the application of this phenomenon to the self-assembly of nanoparticles in a lattice-lie array on a substrate. Issues associated with depositing the particles, and the size and lattice spacing of the particles are discussed.

Carrier Concentration And Lattice Absorption In Bulk And Epitaxial Silicon Carbide Determined Using Infrared Ellipsometry, Thomas E. Tiwald, John A. Woollam, Stefan Zollner, Jim Christiansen, R. B. Gregory, T. Wetteroth, S. R. Wilson, Adrian R. Powell

Department of Electrical and Computer Engineering: Faculty Publications

We have measured the dielectric function of bulk nitrogen-doped 4H and 6H SiC substrates from 700 to 4000 cm^-1 using Fourier-transform infrared spectroscopic ellipsometry. Photon absorption by transverse optical phonons produces a strong reststrahlen band between 797 and 1000 cm^-1 with the effects of phonon anisotropy being observed in the region of the longitudinal phonon energy (960 to 100 cm^-1). The shape of this band is influenced by plasma oscillations of free electrons, which we describe with a classical Drude equation. For the 6H-SiC samples, we modify the Drude equation to account for the strong effective …

Parallel Ac-Ac Converters Using Stationary Master Slave Control, Taufik, F. E. Villaseca

Electrical Engineering

This study proposes parallel ac-ac converters using Stationary Master Slave Control with Sinusoidal Pulse Width Modulation to achieve voltage regulation and equal current sharing among parallel generators such that it minimizes the total production cost. Development of Pspice model representing the parallel ac-ac converters is presented and then simulated. In addition, computer simulations are also used to perform robustness study on the parallel converters.

Temperature Dependence Of Electrical And Optical Modulation Responses Of Quantum-Well Lasers, T. Keating, Xiaomin Jin, Shun Lien Chuang, K. Hess

Electrical Engineering

We present theory and experiment for high-speed optical injection in the absorption region of a quantum-well laser and compare the results with those of electrical injection including the carrier transport effect. We show that the main difference between the two responses is the low-frequency roll-off. By using both injection methods, we obtain more accurate and consistent measurements of many important dynamic laser parameters, including the differential gain, carrier lifetime, K factor, and gain compression factor. Temperature-dependent data of the test laser are presented which show that the most dominant effect is the linear degradation of differential gain and injection efficiency …

Evaluation Of The Transport Properties Of Gasb For Bipolar Applications Through Monte Carlo Simulations, Damayanthi Palaniappan

Electrical & Computer Engineering Theses & Dissertations

GaAs is currently the semiconductor material of choice for high speed, low power applications. Its electronic transport properties are superior to almost all other semiconductors. It is also used in a variety of bipolar applications such as photodetectors and photo-mixers. However, as is well known, the hole mobility and related transport parameters of GaAs are not very good. This is a serious drawback, and poses a potential problem for all applications involving bipolar conductivity. In order to increase the high :frequency limits and high-speed capability of bipolar devices, the choice of an alternative material, therefore, becomes necessary. An important first …

A Pressure Transducer Using Field Emitter Arrays, Mark David Richmond

Electrical & Computer Engineering Theses & Dissertations

A new pressure sensing device using field emission from diamond coated silicon tips has been developed. A high electric field applied between a nano-tip array and a diaphragm configured as electrodes produces electron emission governed by the Fowler - Nordheim equation. The electron emission is very sensitive to the separation between the diaphragm and the tips, which is fixed at an initial spacing and bonded such that a cavity is created between them. Pressure applied to the diaphragm decreases the spacing between the electrodes, thereby increasing the number of electrons emitted.

Silicon has been used as a substrate on which …

Theory Of Photon Coincidence Statistics In Photon-Correlated Beams, Majeed M. Hayat, Sergio N. Torres, Leno M. Pedrotti

Electrical and Computer Engineering Faculty Research and Publications

The statistics of photon coincidence counting in photon-correlated beams is thoroughly investigated considering the effect of the finite coincidence resolving time. The correlated beams are assumed to be generated using parametric downconversion, and the photon streams in the correlated beams are modeled by two partially correlated Poisson point processes. An exact expression for the mean rate of coincidence registration is developed using techniques from renewal theory. It is shown that the use of the traditional approximate rate, in certain situations, leads to the overestimation of the actual rate. The error between the exact and approximate coincidence rates increases as the …

Optical Gain Measurements Based On Fundamental Properties And Comparison With Many-Body Theory, T. Keating, S. H. Park, J. Minch, Xiaomin Jin, Shun-Lien Chuang, T. Tanbun-Ek

Electrical Engineering

We present high accuracy measurements of gain, loss, and transparency energy in long-wavelength semiconductors based on a hybrid approach using the fundamental relationship between the gain and the spontaneous emission spectra. Independent measurements of optical gain, transparency energy, and loss show the accuracy and validity of this technique. These results are compared with those obtained by the non-Markovian gain model with many-body effects under the spontaneous emission transformation method. It is found that the hybrid approach for the gain spectrum alleviates many of the problems related to the poor signal to noise ratio in the amplified-spontaneous emission near and below …

System And Method For Improving Data Acquisistion Capability In Spectroscopic Rotatable Element, Rotating Element, Modulation Element, And Other Ellipsometer And Polarimeter And The Like Systems, Steven E. Green, Craig M. Heringer, Blaine D. Johs, John A. Woollam, Stephen P. Ducharme

Department of Electrical and Computer Engineering: Faculty Publications

Disclosed is a System and method for controlling polarization State determining parameters of a polarized beam of light in an ellipSometer or polarimeter and the like System, (e.g. a modulation element ellipsometer System), So that they are in ranges wherein the Sensitivity, (of a Sample system characterizing PSI and DELTA value monitoring detector used to measure changes in Said polarization State resulting from interaction with a “composite Sample System,” comprised of a Sample System per Se.. and a beam polarization State determining variable retarder, to noise and measurement errors etc. therein), is reduced. The present invention allows determining Sample System …

Implementation And Performance Of Error Correction Codes For High-Speed Computer Networks, Jochen Spengler

Dissertations and Theses

During the transmission of data there is always a possibility that errors occur and some pieces are modified. If the receiver detects an error it either sends a request for retransmission or, like in networks using Ethernet, it does not send an acknowledgment for the erroneous frame. In this case the sender waits a certain time and retransmits the frame. With the development of faster computer networking hardware and the need for more real-time applications, these errors have become a major concern. Long retransmission latencies and the need for large memories for buffering drive the development of more reliable network …

Optoelectronic Switching Network With 2d Optical Fiber Bundle Array I/O Access Device, Fengguang Luo, Mingcui Cao, Qiaoyan Hu, Anjun Wan, Jun Xu, Cong Deng, Yuan-Zhong Xu

Electro-Optics and Photonics Faculty Publications

An optoelectronic switching network with 2-D optical fiber bundle arrays I/O access device is presented in this paper. An optoelectronic recirculating Banyan network based on CMOS/SEED smart pixel device is used in this configuration. Thirty-two X two single-mode fiber bundle array and 32 X 2 multi- mode fiber bundle array are fabricated respectively based on the features of high density, high precision and array permutation of the CMOS/SEED optoelectronic integrated devices. The measuring results show that the center to center spacing between adjacent optical fibers in the same layer of the fiber array is 125 micrometer, and the spacing between …

Optical Constants Of Crystalline Wo3 Deposited By Magnetron Sputtering, Michael J. Devries, Chris Trimble, Thomas E. Tiwald, Daniel W. Thompson, John A. Woollam, Jeffrey S. Hale

Department of Electrical and Computer Engineering: Faculty Publications

Crystalline WO_3-x is an infrared (IR) electrochromic material having possible applications in satellite thermal control and IR switches. Optical constants of electrochromic materials change upon ion intercalation, usually with H⁺ or Li⁺. Of primary concern for device design are the optical constants in both the intercalated and deintercalated states. In situ and ex situ ellipsometric data are used to characterize both the deposition process and the optical constants of the films. Ex situ data from a UV-Vis-NIR ellipsometer are combined with data from a mid-infrared Fourier-transform-infrared-based ellipsometer to provide optical constants over a spectral range …

Double-Pass High-Gain Laser Amplifiers, Janet M. Casperson, Frederick G. Moore, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Double-pass laser amplifiers have advantages of compactness and efficiency in the amplification of optical signals, and such amplifiers have been employed in a wide range of optical systems. Work in this area is reviewed briefly, and analytical solutions are obtained for the intensity of the electromagnetic waves in double-pass homogeneously-broadened high-gain laser amplifiers. Expressions are derived relating the output power to the input, including the effects of arbitrary mirror reflectivity and frequency detuning from line center. In the limits of weak saturation and of high reflectivity the results are consistent with earlier studies.

Detection And Robustness Of Digital Image Watermarking Signals : A Communication Theory Approach, George F. Elmasry

Dissertations

The detection and robustness of the watermark signal is studied from a communications point of view. The contributions of this dissertation are presented in two parts. The first part, which covers the detection aspect, introduces a new digital image watermarking approach that embeds meaningful information in a copyright protection watermark signal; demonstrates the need to approach the watermark signal as a power-constrained signal; studies the relationship between the watermark signal dimension and the image capacity to the signal; explains the similarities and differences between detecting the watermark signal and detecting a signal over a spread-spectrum communication channel; and analyzes the …

Emissivity Measurements And Modeling Of Silicon Related Materials, Vijay Krishnamurthy

Theses

The objective of the thesis was to study the radiative properties of silicon related materials for applications in rapid thermal proceesing. In particular, three distinct materials have been considered - Silicon, SIMOX and Tantalum.

The research highlights are Establishment of spectral emissometry as a novel, reliable and reproducible technique for a) Determination of wavelength and temperature dependent reflectivity, transmissivity, emissivity of silicon related materials and structures. The emissometer operates in the wavelength range of 1-20µm and temperature range of 300-1200K. b) Establishment of methodoligies to obtain the frnndemental constants. Effects of wavelength, temperature, total available free carriers by doping types …